1. Field of the Invention
The present invention relates to a ball screw device or motion guide apparatus, and more particularly to a ball screw device including a lubricating device attached to a movable nut member for applying a lubricating grease or oil onto the movable nut member and for suitably lubricating the movable nut member and for allowing the movable nut member to be smoothly moved relative to the elongated shaft.
2. Description of the Prior Art
Typical ball screw devices or linear motion guide apparatuses comprise a movable member, such as a movable nut member rotatably or movably engaged onto the longitudinal screw shaft and movable relative to each other, and a number of ball bearing elements disposed between the movable nut member and the screw shaft for facilitating the sliding movement between the movable nut member and the screw shaft.
For example, U.S. Pat. No. 5,782,135 to Kondo et al. discloses one of the typical ball screw devices comprising a ball nut pivotally or rotatably coupled onto a screw shaft, and a number of loaded ball bearing elements disposed between the screw shaft and the ball nut for facilitating the sliding movement between the screw shaft and the ball nut, and a number of non-loaded balls disposed between the loaded ball bearing elements and made of lubricating materials for suitably lubricating the loaded ball bearing elements and the screw shaft and the ball nut.
However, after use, the non-loaded balls will be worn out and will have a reduced outer diameter such that the gaps between the loaded ball bearing elements will be greatly increased and such that the screw shaft and the ball nut may not be suitably pivoted or rotated relative to each other.
U.S. Pat. No. 6,015,775 to Takayama et al., and U.S. Pat. No. 6,068,931 to Adam et al. disclose two further typical self-lubricating sliding or bearing materials made of specially designed or selected elements for suitably lubricating two movable or rotatable or slidable members.
However, the specially designed or selected elements may greatly increase the manufacturing costs for the sliding or bearing materials.
U.S. Pat. No. 7,234,368 to Lin et al. discloses a further typical ball screw device comprising a ball nut pivotally or rotatably coupled onto a screw shaft, and a number of ball bearing elements disposed between the screw shaft and the ball nut for facilitating the sliding movement between the screw shaft and the ball nut, and one or more guide members engaged in the helical groove portions of the screw shaft and each having an oil retaining member for applying the oil onto the screw shaft.
However, the ball nut should be specially designed and machined for fitting or mounting the guide members such that the manufacturing procedures for the typical ball screw device will be complicated and such that the manufacturing costs for the typical ball screw device will be greatly increased.
U.S. Pat. No. 8,387,474 to Lin et al. discloses a further typical ball screw device comprising a ball nut pivotally or rotatably coupled onto a screw shaft, and a number of ball bearing elements disposed between the screw shaft and the ball nut for facilitating the sliding movement between the screw shaft and the ball nut, and a lubricating device attached to the ball nut for applying a lubricating grease or oil onto the ball nut and for suitably lubricating the movable nut members.
However, the typical screw devices have no suitable structure for effectively supplying or applying the lubricating grease or oil to the screw shaft and the ball nut.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional ball screw devices or motion guide apparatuses.